WASHINGTON — NATO warplanes destroyed the oldest and most heavily used bridge over the Danube River in the northern town of Novi Sad on Thursday, cutting shipping on the important European waterway as pilots expanded their search for targets in the bid to force Yugoslavia to end its purge of ethnic Albanians from Kosovo province.

In London, British diplomats said there were signs of a split in the Yugoslav military between factions supporting President Slobodan Milosevic's campaign against the ethnic Albanians and senior officers who disagree with the policy.

"Not all his senior commanders want to pay the same price as Milosevic. We are getting early reports of sacking of senior military commanders," British Foreign Secretary Robin Cook said. "Perhaps they are worried about the prospects of a war crimes trial . . . or they are honorable men revolted by what they are being asked to do."

As NATO warplanes and cruise missiles hit targets in northern towns and around the Kosovar capital of Pristina, the human toll continued to climb.

Tens of thousands of refugees poured into Albania, Macedonia and Montenegro, with two trains carrying an estimated 10,000 refugees to the Macedonian border alone on Thursday.

Western military planes loaded with relief supplies arrived in Albania to ease the refugee crisis.

Four relief planes arrived at the capital of Tirana at noon and an Italian naval vessel laden with water trucks and military field kitchens moored in the Adriatic port of Durres.

The United Nations High Commissioner for Refugees, the UN Children's Fund and other relief organizations sent medicine, blankets, food and tents.

British military officials said bad weather interfered with much of the air campaign Thursday.

"We would desperately like to proceed faster in order to bring the killings to an end more quickly, but we will not take senseless risks, either with civilian casualties or with the lives of our airmen," said British Air Vice Marshal John Day.

He said the NATO attacks had so severely depleted fuel supplies in Yugoslavia that the government was requisitioning all diesel fuel coming into the country. Day also said the Yugoslav army's ammunition supplies have been hit hard.

"The ring is closing around the Yugoslav forces," said NATO Secretary General Javier Solana.

The Yugoslav government has charged the NATO attacks are illegal and said refugees are actually fleeing NATO pilots, not Serb army and police units.

NATO military planners announced two days ago that they had shifted to a new phase in the air war against Milosevic, the Yugoslav army and the Interior Ministry special police who are believed to be playing the most active, and the most brutal, role in forcing the ethnic Albanians out of Kosovo.

The attack on the bridge in Novi Sad was the first sign in the nine-day-old campaign that the focus of the raids was shifting from distant military districts and army installations to civil facilities much closer to population centers.

The old bridge carried important psychological and emotional weight in Novi Sad, a resident told Serbian television crews.

A collection of military warehouses sits at one end of the bridge, according to Serbian media. Debris from the destroyed bridge also blocked passage on the Danube, cutting access to the Black Sea and trapping four Bulgarian freighters about to sail home.

Demands continued for negotiations to end the bombing.

The Vatican's foreign minister, Archbishop Jean-Louis Tauran, met with Milosevic and other leaders in Belgrade on Thursday.

"His Holiness (Pope John Paul II) and many Christian leaders . . . consider that it would be a gesture of great humanity if all military actions would be suspended by all during the week which separates the Western and Eastern commemoration of this feast (Easter), from April 4 to April 11," Tauran said.

"Of course, such an initiative should be accompanied by practical measures on the ground so that no one would take advantage of this period . . ."